Sensor device for a motor vehicle used for detecting environmental parameters

ABSTRACT

The invention relates to a sensor device for a motor vehicle used for detecting environmental parameters. The sensor has at least one camera system. At least two camera systems are used, each operating in a different region of the electromagnetic spectrum in order to improve the functionality of such a sensor device.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a sensor arrangement for a motor vehicle fordetecting an environment having at least two camera systems.

A sensor system of this type can be used, for example, for assisting thedriver, thus for supporting an operator of a vehicle. It suppliesinformation on the environment and can be used in the domain of lanetracking, for a warning in the case of a lane deviation, or in thedomain of automatic vehicle guidance.

In the case of such sensor systems, it is known to use so-called CCDcameras (CCD=charged coupled device). However, it should be taken intoaccount that the functionality of driving assistance systems is limitedwhen the sensor is already subjected to limitations when detecting theenvironment. In the case of CCD cameras, it is known that, especially indarkness and in the event of blinding due to an external light source,these cameras have a limited functionality. In this case, with respectto a blinding light in darkness, a superproportional limitation shouldbe taken into account, specifically when the CCD camera is adjusted tothe environmentally caused illumination level. In the event anothervehicle driving with switched-on lights is encountered, the imageinformation is even largely destroyed by the oncoming blinding lightsources.

The use of infrared cameras in such sensor arrangements is also known(see. e.g. technical journal: CAR AND DRIVER, October 1998). Infraredcameras obtain a heat image of the driving environment. In the heatimage, all contours and objects are based on thermal contrasts. However,the information which is important for the driving task or for thereaction of a driver assistance system cannot always be obtained fromthe heat image.

European patent document EP 0 454 516 A1 describes an obstacle detectionsystem having two video cameras, which generate images in the visibleand in the infrared range. For generating images in the infrared range,CCD technology is used, for example. By means of a similar video camera,which can detect the entire spectrum, a differential signal isgenerated. This differential signal or differential image relates to thevisual range, which is covered by the cameras and is based on thecontrast of an object in this visual range. Japanese patent documentJP-10 255019 also describes a system with a CCD camera, which generatesa visible image from the area in front of a vehicle. Furthermore, aninfrared image is generated by an additional infrared camera. Based onthe temperature information, a threshold for illuminated parts isgenerated, and an improved vehicle detection can take place on the basisof this threshold.

It is an object of the present invention to further develop a sensorarrangement of the above-mentioned type such that the environment can bedetected essentially without any limitation of the functionality.

This object is achieved by a sensor arrangement for a motor vehicle fordetecting the environment using at least two camera systems. Each camerasystem operates in a different spectral region. Each camera system isadjusted to obtain images in different distance ranges.

An essential idea of the invention is to use at least two camera systemswith respectively different spectral operating regions.

In this case, the different camera systems are adjusted to differentdistance ranges. For example, an infrared camera takes over theenvironmental detection in the remote range because it is suitable forday and night use and is free from the effects of blinding. Freedom fromblinding means, in this context, that the individual pixels are notovermodulated by the headlights of oncoming vehicles. The imageinformation is therefore retained although the environment is completelydark. The close range is detected by the CCD camera. In particular, theCCD camera is adjusted such that it operates in a range which isilluminated by the front headlights when the vehicle headlights areswitched on. Because of the higher illumination level, this measurereduces the susceptibility of the CCD camera to blinding effects.

According to a preferred embodiment, the sensor arrangement comprises aCCD-camera (charged coupled device) and a camera which operates in theinfrared range. The infrared camera represents, for example, ameaningful supplementation of the sensor system (CCD), which is visualhere, beyond its detection limits in the extended area in front of thedriving environment.

When using camera systems adjusted to different distance ranges and withconnected imaging scales, the driving environment, as a whole, can bedetected better in both the close and remote ranges.

Another advantage of using two camera systems with different spectraloperating regions consists of determining the atmospheric absorbance inthe two spectral regions via differential contrast evaluation, acomparison of differences in contrast between objects and theirenvironments. Because atmospheric absorbances have different effects onimages formed by different camera systems adjusted to different distanceranges, by comparing differences in contrast observed by the differentcamera systems (which are indicative of the atmospheric absorbances),conclusions can be drawn with respect to the extent of fog or haze.Furthermore, in conjunction with a visual range model stored in avehicle, a driver's visual range can be determined from the detectedabsorbances. This information, in turn, can be made available to thedriver, or control parameters can be adjusted in the vehicle as afunction of the determined driver's visual range.

These and other advantageous embodiments are defined in the subclaims.

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE will be explained in detail in the following and withreference to the single drawing. The FIGURE of the single drawing is aschematic top view of a vehicle with a sensor system according to theinvention arranged on the front of the vehicle.

DETAILED DESCRIPTION OF THE DRAWING

A vehicle 10 has two headlights 12, which illuminate a certain lightrange L during operation.

Between the two front headlights 12, two cameras are arranged,specifically in this case, an infrared camera 16 and a CCD camera(CCD=charged coupled device) 14. Both cameras 16 and 14 are aligned inthe driving direction. The CCD camera is constructed and adjusted suchthat it essentially detects the range A, which is illuminated when thefront headlights are switched on and therefore corresponds to the rangeL.

In contrast, the infrared camera 16 detects the environment particularlyin the remote range B.

Both cameras 16, 14 are connected with a control and analyzing device18. The control and analyzing device 18 emits a signal to a display 20,which is arranged in the interior of the vehicle within the driver'sviewing range. The display 20 informs the driver of the environmentalsituation in the detected ranges.

In addition, but not shown in the FIGURE, the control and analyzingdevice 18 can supply its information also to other units in the vehicle,for example, to systems concerned with automatic vehicle guidance.

On the one hand, the control and analyzing device 18 forwards theinformation transmitted by the cameras 16 and 14 directly to the driver.It also carries out a differential contrast evaluation. As a result, theatmospheric absorbance can be determined in the two spectral regions. Ifa visual range model is also stored in the control and analyzing device18, by way of the detected absorbances and by means of a differentialcontrast evaluation, a conclusion can also be drawn with respect to thedriver's visual range.

This visual range and/or these detected absorbances can then be utilizedfor adapting control parameters or for recommending a vehicle speed tothe driver.

However, for determining the atmospheric absorbance in the visiblespectral region, another system, such as a light detection and ranging(LIDAR) system may also be used.

A memory device 22 can be provided in which a visual range model isstored. A device 24 is provided by which a conclusion can be drawn withrespect to the visual range from information of the analyzing device 18.

1. A motor vehicle sensor system for detecting an outer environment, thesensor system comprising: at least two camera systems operable to imagethe outer environment; and wherein each camera system operates in adifferent spectral region and is adjusted to a different distance range.2. The sensor system according to claim 1, wherein one of said at leasttwo camera systems is an infrared camera operating in an infrared range.3. The sensor system according to claim 2, wherein another of said atleast two camera systems is a CCD camera.
 4. The sensor system accordingto claim 3, wherein the CCD camera distance range is for detectionwithin a close range.
 5. The sensor system according to claim 4, whereinthe close range substantially corresponds with a headlight cone range ofa vehicle driven with its headlights on.
 6. The sensor system accordingto claim 1, wherein one of said at least two camera systems is a CCDcamera.
 7. The sensor system according to claim 6, wherein the CCDcamera distance range is for detection within a close range.
 8. Thesensor system according to claim 7, wherein the close rangesubstantially corresponds with a headlight cone range of a vehicledriven with its headlights on.
 9. The sensor system according to claim1, further comprising an analyzing device operatively coupled with saidat least two camera systems and receiving inputs therefrom.
 10. Thesensor system according to claim 9, wherein said analyzing deviceincludes means for performing differential contrast evaluation.
 11. Thesensor system according to claim 10, further comprising: a memory devicein which is stored a visual range model; and a visual range determiningdevice operatively coupled to the memory device, said visual rangedetermining device operating to draw a conclusion with respect to avisual range from information from the analyzing device.
 12. The sensorsystem according to claim 11, wherein said information from theanalyzing device is differential contrast evaluation information. 13.The sensor system according to claim 9, further comprising: a memorydevice in which is stored a visual range model; and a visual rangedetermining device operatively coupled to the memory device, said visualrange determining device operating to draw a conclusion with respect toa visual range from information from the analyzing device.
 14. Thesensor system according to claim 13, wherein said information from theanalyzing device is differential contrast evaluation information.
 15. Amotor vehicle, comprising: a vehicle body; at least two camera systemsarranged in a forward portion of the vehicle body for imaging areas in atraveling direction of the motor vehicle; wherein each of said at leasttwo camera systems has a different spectral operating region; andfurther wherein each of said at least two camera systems is adjusted toa different distance range in the traveling direction.
 16. The motorvehicle according to claim 15, wherein one of said at least two camerasystems is an infrared camera operating in an infrared spectral region.17. The motor vehicle according to claim 16, wherein another of said atleast two camera systems is a CCD camera.
 18. The motor vehicleaccording to claim 17, wherein said CCD camera distance rangecorresponds with a headlight cone range of a headlight arranged in theforward area of the vehicle.
 19. The motor vehicle according to claim15, wherein one of said at least two camera systems is a CCD camera. 20.The motor vehicle according to claim 19, wherein said CCD cameradistance range corresponds with a headlight cone range of a headlightarranged in the forward area of the vehicle.
 21. The motor vehicleaccording to claim 15, further comprising an analyzing deviceoperatively coupled to said at least two camera systems, said analyzingdevice outputting a display signal.
 22. The motor vehicle according toclaim 21, further comprising a display arranged in an interior of thevehicle within a driver's viewing range, said display receiving thedisplay signal from the analyzing device to provide environmentalsituation information to the driver.